The present invention is concerned with apparatus for handling bulky articles at sea, particularly, but not exclusively, for handling modules such as pipeline end terminations (PLETs) and in-line tee's (ILTs) around the deck of a pipe laying vessel.
On offshore structures such as oil rigs, pipe laying vessels, drilling vessels, etc. it is often necessary to manoeuvre large bulky articles from one area of the structure to another. An example of when this is necessary is when a module such as a PLET or ILT is moved from a storage area to the firing line of a pipe laying vessel. On typical vessels, movement of the module normally involves using a crane (or series of cranes) to pick up the module clear of the vessel's deck, move it to a point above the desired end position, and then lower the module to that position. However, such crane based systems have a number of disadvantages. The procedure of connecting the crane to the module, moving it to the desired position and lowering the module to the correct position can be slow and difficult to replicate accurately. Furthermore, the process must often take place when a very limited amount of time is available to move the module into position.
The vertical distance by which the module must be raised, combined with the inherent movement of the vessel in the sea causes the module to swing around on the crane in a fashion which can be difficult to control safely. This results in such crane based methods being unsuitable for use in poor weather conditions, leading to unreliability and inefficient use of resources.
According to a first aspect of the present invention, there is provided apparatus for handling bulky articles on a deck of a vessel at sea, the apparatus comprising:                a cradle for supporting the bulky article;        first translational movement means provided between the deck and the cradle;        second translational movement means moveable along the deck, wherein the first translational movement means allows the bulky article to be moved from a storage area and transferred to the second translational movement means, and the second translational movement means allows the bulky article on its cradle to be moved toward an operational location; and        at least one actuator provided between the deck and the cradle, the actuator being operable to adjust the orientation of the bulky article relative to the deck, when in said operational position.        
The apparatus may be provided on a pipelaying vessel and allows the article to be transferred from storage to its operational position, which may be the pipe laying axis, without using a crane to lift the articles into position on the deck of the structure and, once it is at an operational location, allows the bulky article to be orientated and accurately aligned using the actuator as required. This is particularly useful for moving a module, such as a PLET or ILT, from a storage area to a firing line of a pipe laying vessel, since very accurate alignment of the PLET or ILT with the pipeline must be achieved in order to allow them to be connected together by, for example, welding. Such alignment generally will require tilting the article in one or two planes perpendicular to the deck.
The actuator may be arranged between the cradle and the translational movement means. Alternatively the actuator could act between the deck and the translational movement means, the latter moving with the cradle and article together. Alternatively, the actuator may comprise an actuator discrete from the translational movement means such that the actuator may act directly between the cradle and the vessel. In such an embodiment, the translational movement means may return to a storage/retrieving position whilst the discrete actuator performs the alignment process.
The first and/or second translational movement means may include propulsion means operable to move the bulky article. Alternatively they may be passive devices, moved by externally applied force.
The apparatus preferably includes a plurality of cradles compatible with the translational movement means. By using the intermediary of the cradle, the interface to the movement means can be standardised, while handling many forms of module.
The apparatus may include releasable couplings for anchoring the cradles on deck during transit. The modules to be installed can be pre-assembled onto respective cradles prior to loading the vessel, which saves time in port.
In a preferred embodiment, the first translational movement means provides for skidding of the cradle into position for transfer to the second translational movement means, while the second translational movement means comprises a wheeled frame. The first translational movement means may include transverse rails which allow the cradle to move laterally to and from the vessel centreline and hence to and from the bulky article. A grabbing mechanism which allows the bulky article to be grabbed and slid away from its storage position and onto the transverse rails may also be provided.
References to translational movement are not to be interpreted so strictly as to exclude excluding rotational motion in addition. For example, the first translational movement means may comprise a carousel or turntable, for bringing each cradle/article into engagement with the second translational movement means.
The apparatus may include a plurality of skidding frames each being arranged to interface between a respective cradle and the deck, the skidding frame forming part of the first translational movement means in respect of its respective cradle.
Typically, the operational location is in the pipe laying vessel firing line, so that articles from the storage location can be connected into a pipeline being laid.
The first movement means may be arranged to move said cradle transversely of a centre line of the vessel, while the second translational movement means is arranged to move the cradle longitudinally, that is parallel to the centre line, in order to reach said operational location.
The second translational movement means may comprise a trolley and rails on which the trolley may be driven to said operational location. In a preferred embodiment, the trolley is capable of selectively interlocking with the skidding frame in order to selectively deposit the skidding frame at said first or second longitudinal locations. The interlocking capability may be provided by a pickup mechanism which selectively lifts and lowers the skidding frame to and from a seated position on the deck.
Clearly, the stroking movement of the apparatus requires a portion of the deck space to be cleared from any obstructions. In order to compensate for any resulting decrease in overall deck space available for other operations, there may be provided a channel in the deck, running between the rails along the path of the trolley. A hatch cover, which may comprise part of the skidding frame, may be provided to cover said recess when the trolley is not in use.
In one embodiment, the longitudinal channel is provided substantially along the centre line of the vessel and runs in a fore to aft direction.
The actuator may be provided on the trolley and be capable of actuating the bulky article between upper and lower positions. The actuator may be further capable of actuating between extended and retracted positions in order to actuate the bulky article between fore and aft longitudinal positions.
The actuator may comprise a pair of engagement arms which are telescopically moveable hydraulic arms having a hinged connection to the trolley at one end and a U-shaped engagement bracket at the other end for connection to a corresponding attachment on the cradle.
The actuator allows the orientation of the bulky article to be adjusted relative to the deck of the vessel. This is useful, for example, to assist connection of the bulky article to the pipeline being laid by allowing it to be angled in line with the catenary thereof.
The first translational movement means provided between the cradle and the deck preferably comprises friction reduction means provided on the cradle and corresponding friction reduction means provided on the deck. The friction reduction means may comprise skidding pads on the deck and/or cradle and corresponding skidding rails on the deck and/or cradle. Preferably, the skidding pads and/or rails provided on the deck are releasably secured to the deck in order to allow spacing of the bulky articles in the storage area to be adjusted.
The apparatus may comprise drive means for urging the cradle item from the storage area on the deck onto the second translation movement means. Typically, the drive means comprises a winch and pulley system provided on and moveable with the second translational movement means. Alternatively, one or more short-throw rams may be provided to move the cradle step-wise by repeated operation of the ram.
Preferably, the cradle comprises an L-shaped support in order to provide a support ledge for supporting a lower end of the bulky item and a support back for supporting the length of the bulky article. This minimises the footprint of the bulky article on the deck of the structure. The support ledge and support back may be substantially planar in form, so as to accommodate a wide range of modules on the same form of cradle.
According to the first aspect of the present invention, there is further provided a method of handling bulky articles on a deck of a vessel at sea, the method comprising:                storing in a supporting cradle at least a bulky article in a storage area on first translational means provided between the cradle and the deck of the structure;        providing second translational movement means at a loading location adjacent the bulky article;        sliding the bulky article over the first translational movement means, and onto the second translational movement means;        moving the translational means from the loading location to an operational location; and        adjusting the orientation of the bulky article relative to the deck using at least an actuator provided between the second translational movement means and the bulky article.        
The bulky article may comprise a module such as a PLET or ILT to be installed in a pipe line being laid by the vessel.
The step of moving the second translational movement means along the deck may be performed using a trolley moveable from a first longitudinal location on the deck to a second longitudinal location on the deck.
The method may preferably include the step of storing a plurality of bulky articles on their cradles in the storage area of the deck to allow random access to a particular bulky article on its cradle by moving the second translational movement means to a location along the deck adjacent the particular bulky article required. The plurality of bulky articles may be stacked on one end thereof in order to reduce their footprint on the deck of the vessel.
The method may further include the step of returning the second translational movement means to a further loading location adjacent a further bulky item upon deployment of the first bulky article on its cradle at the operational location.
Optionally, the method includes selective lowering of the bulky article using the actuator in order to allow it to pass by certain structures on the vessel, for example, between the legs of a pipe-laying tower.
The method may include an initial step of placing the bulky articles on the deck of the vessel in a single operation where the bulky article, cradle and at least part of the first translational movement means are all secured together in a unit which may be lifted onto the deck of the vessel in a single lifting operation.
The step of adjusting the orientation of the bulky article on its cradle relative to the deck using at least an actuator may comprises the step of actuating the bulky article on its cradle between upper and lower positions and actuating the bulky article between extended and retracted longitudinal positions.
The step of sliding the bulky article on its cradle over the first translational movement means may optionally comprise moving the bulky article from the storage area on the deck onto the second translational movement means using drive means such as a winch and pulley system provided on and moveable with the second translational movement means.